To analyze the possible influence of 60 GHz millimeter waves on the physical properties of phospholipid layers in artificial models of biological membranes.
Two principal phospholipid components of biological membranes were used: dipalmitoylphosphatidycholine (DPPC) and dioleoylphosphatidylcholine (DOPC). The role of different irradiation parameters was examined (e.g. power flux density, magnetic field strength).
In the first part of the study, the effect of millimeter waves on superficial pressure of phospholipid monolayers was investigated. In the second part, the microdomain distribution in mixed phospholipid monolayers with phase separation was studied. Microdomains reflect functional specialization of the different membrane regions and play an important role in membrane interaction processes.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
60 GHz
Modulation type:
CW
Exposure duration:
continuous for 5 h
|
|
|
Exposure 2:
60 GHz
Modulation type:
AM
Exposure duration:
continuous for 5 h
|
|
|
Exposure 3:
60 GHz
Modulation type:
CW
Exposure duration:
intermittend 1 h on - 1 h off for 7 h
|
|
|
Exposure 4:
60 GHz
Modulation type:
CW
Exposure duration:
continuous for 3 h
|
|
|
Exposure 5:
60 GHz
Modulation type:
CW
Exposure duration:
continuous for 5 h
|
|
For exposures 1 - 4 dipalmitoylphosphatidylcholine (DPPC) membranes in the liquid-condensed (LC) phase with an average superficial pressure of 28.5-32 mN/m were used. In exposure 5 a biphase DPPC monolayer was studied with an initial superficial pressure of 18.2 mN/m. Under normal environmental conditions, this value corresponds to liquid condensed/liquid-expanded (LC/LE) phase separation in DPPC monolayers.
| Frequency | 60 GHz |
|---|---|
| Type | |
| Charakteristic | |
| Polarization |
|
| Exposure duration | continuous for 5 h |
| Modulation type | CW |
|---|
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 82.4 V/m | maximum | calculated | - | for 50 mW incident power |
| power density | 0.9 mW/cm² | maximum | calculated | - | for 50 mW incident power |
| magnetic field strength | 0.219 A/m | maximum | calculated | - | for 50 mW incident power |
| power density | 0.009 mW/cm² | maximum | calculated | - | for 0,5 mW incident power |
| electric field strength | 8.2 V/m | maximum | calculated | - | for 0,5 mW incident power |
| magnetic field strength | 0.022 A/m | maximum | calculated | - | for 0,5 mW incident power |
| Frequency | 60 GHz |
|---|---|
| Type | |
| Waveform |
|
| Charakteristic | |
| Polarization |
|
| Exposure duration | continuous for 5 h |
| Modulation type | AM |
|---|---|
| Modulation frequency | 1 kHz |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 58.3 V/m | maximum | calculated | - | - |
| magnetic field strength | 0.155 A/m | maximum | calculated | - | - |
| power density | 0.45 mW/cm² | average over time | calculated | - | - |
| Frequency | 60 GHz |
|---|---|
| Type | |
| Charakteristic | |
| Polarization |
|
| Exposure duration | intermittend 1 h on - 1 h off for 7 h |
| Modulation type | CW |
|---|
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 0.45 mW/cm² | maximum | calculated | - | - |
| electric field strength | 58.3 V/m | maximum | calculated | - | - |
| magnetic field strength | 0.155 A/m | maximum | calculated | - | - |
| Frequency | 60 GHz |
|---|---|
| Type | |
| Charakteristic | |
| Polarization |
|
| Exposure duration | continuous for 3 h |
| Modulation type | CW |
|---|
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 0.36 mW/cm² | maximum | calculated | - | - |
| electric field strength | 57.6 V/m | maximum | calculated | - | - |
| magnetic field strength | 0.153 A/m | maximum | calculated | - | - |
| Frequency | 60 GHz |
|---|---|
| Type | |
| Charakteristic | |
| Polarization | |
| Exposure duration | continuous for 5 h |
| Modulation type | CW |
|---|
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 0.41 mW/cm² | maximum | calculated | - | - |
| magnetic field strength | 0.0147 A/m | maximum | calculated | - | - |
| electric field strength | 55.5 V/m | maximum | calculated | - | - |
Measurements of superficial pressure of phospholipid monolayers have shown weak but reproducible variations, essentially determined by superficial power flux density incident onto the membrane. Even very low power flux density levels resulted in a marked increase of lateral pressure. All other exposure parameters did not show a signifcant influence.
The AFM analysis has evidenced that low-power millimeter wave irradiation does not induce significant transformations in the phospholipid domain organization in model membranes.
The biophysical properties of phospholipid layers of biological membranes could be partly modified by low-power millimeter wave irradiation.
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